Higher prevalence of intentional self-harm in bipolar disorder with evening chronotype: A finding from the APPLE...

Patients with bipolar disorder (BD) frequently self-harm, and this is strongly associated with subsequent suicide. This study investigated the association between chronotype and intentional self-harm in patients with BD.

Two-hundred and five outpatients with BD participated in this cross-sectional study. Each participant's chronotype was evaluated using the Morningness-Eveningness Questionnaire, dividing the scores into three types: evening, 16-41 points; intermediate, 42-58 points; and morning, 59-86 points. Intentional self-harm over the past year were self-reported by questionnaire. Propensity score for evening chronotype was estimated from age, sex, socioeconomic factors, mood symptoms, total sleep time, age at the onset of BD, psychiatric inpatient history, family history of suicide, psychiatric comorbidity, and use of lithium.

Thirty-six (18%) of the 205 participants reported self-harm. A substantially higher proportion of the evening chronotype group self-harmed compared to the other groups (evening, 37%; intermediate, 13%; morning 10%). In multivariable analysis adjusted for propensity score, the odds ratio (OR) for self-harming significantly increased from morning to intermediate to evening chronotype (ORs: morning, 1.00; intermediate, 1.56; evening, 3.61; P for trend = 0.038).

This study was a cross-sectional and small sample size.

Although a third factors, such as personality disorder or disrupted circadian rhythm, may have influenced, these findings suggest association between chronotype and intentional self-harm in BD patients.